In order to calibrate a gas analyzer such as an exhaust gas analyzing system, it is necessary to supply standard gas having a predetermined concentration to the gas analyzer. Also, as a system that produces the standard gas having a predetermined concentration, as disclosed in Patent Literature 1 or the like, there is a standard gas concentration controller system that has: a diluent gas line that is supplied with diluent gas; a standard gas line that is supplied with standard gas having high concentration; and an output gas line that is joined by the diluent and standard gas lines and outputs diluted standard gas having a predetermined concentration to a gas analyzer. In the standard gas concentration controller system, the diluent line is provided with a mass flow controller for controlling a flow rate of the diluent gas, and the standard gas line is provided with a mass flow controller for controlling a flow rate of the standard gas.
However, in the case of using the standard gas concentration controller system having the above configuration to produce the low concentration standard gas, it is necessary to control the flow rate of the standard gas flowing through the standard gas line to a low flow rate with use of the mass flow controller provided in the standard gas line. If doing so, on an upstream side of the mass flow controller in the standard gas line, the standard gas remains. If the standard gas has adsorptive property, there occurs a problem that the standard gas adsorbs onto an inner surface of a pipe constituting the standard gas line. If the standard gas adsorbs onto the inner surface of the pipe as described, a concentration of the standard gas supplied to the output gas line is reduced, and consequently, a concentration of the produced standard gas also becomes lower than the predetermined concentration. Further, there occurs a problem that the gas analyzer calibrated with use of the standard gas is also inaccurately calibrated.
Also, if the pipe constituting the standard gas line is one having gas permeability, such as a Teflon tube, a gas component (such as oxygen) in outside air permeates the standard gas line. If the standard gas is one having a reactive property with a permeating gas component (such as oxygen) and, such as NO gas, there occurs a problem that the standard gas reacts with oxygen to reduce the concentration of the standard gas. If so, the concentration of the standard gas supplied to the output gas line is reduced, and a concentration of the produced standard gas also becomes lower than the predetermined concentration. This causes a problem that the gas analyzer is also inaccurately calibrated.